1. Field of the Invention
The present invention relates to a load drive apparatus having a function of pulse-width modulating a drive signal applied to a load apparatus to be controlled.
2. Description of Related Art
It is known to detect occurrence of a short circuit on a path for connection between a load apparatus and a load drive apparatus that has a switching element for PWM-modulating (pulse-width modulating) a drive signal applied to the load apparatus through this path in accordance with a PWM signal by monitoring the state (voltage level) of the path. If the monitored state does not change when the drive signal is being PWM-modulated in accordance with the PWM signal, it can be determined that a short circuit has occurred on the path. For detail, refer to Japanese Patent Application Laid-open No. 09-196991.
That is because, if the path is short-circuited to a high level side (to a power supply side), the monitored state is fixed at a high level, and if the path is short-circuited to a low level side (to a ground side), the monitored state is fixed at a low level.
It is a matter of course that it can be determined to which side the path has been short-circuited from the monitored state.
Incidentally, in recent years, the switching element is being replaced by a driver unit constituted by a general-purpose IC in order to reduce production costs and to provide additional functions other than the switching function.
However, although such a driver unit can detect occurrence of a short circuit, it cannot determine to which side the path has been short-circuited because of the standardized circuit design of the general-purpose IC. To provide the driver unit with the capability of determining to which side the path has been short-circuited, it is necessary to replace the general-purpose IC with a custom-designed IC. This increases the production costs of the load drive apparatus.